explain this.

So.... My Sweet Darling and I will be laying in bed just cuddle up and basically making out like kids. He will make a moan/sigh imnot sure and out of nowhere pull away from me turn over on his back. I ask whats wrong. what is it. He always says nothing. A few moments pass and he comes back for more. He knows we can take it further at anytime and any where. What the hell is this mans deal.